This invention relates to liquid formulations that can be applied to the surface of a wood-based flooring panel and dried to form a coated product that is suitable for use as a substrate for decorative floor covering. The coating on the panel dramatically inhibits the staining action that occurs when a decorative vinyl floor covering is installed directly over a wooden substrate. The coating system described inhibits the staining action that occurs when oriented strandboard (OSB) underlayment is used in conjunction with vinyl floor sheathing, while simultaneously providing a substrate surface that has exceptional compatibility with the adhesives and patching materials that are commonly used during the process of installing vinyl floor coverings. The coating formulations are stable and resistant to phase separation and settling over storage periods in excess of two months, and they can be used in high-volume commercial coating operations in compliance with current U.S. environmental regulations.
Decorative vinyl floor coverings are commonly installed in residential dwellings in North America. Manufacturers of vinyl floor coverings include Armstrong World Industries (Lancaster, Pa.), Mannington (Salem, N.J.), Congoleum Corporation (Mercerville, N.J.), and Tarkett Incorporated (Whitehall, Pa.). Contemporary floor covering materials are described in U.S. Pat. No. 5,308,694. Although there are a number of elaborate vinyl floor covering construction designs, most are comprised of a three-layered structure. The bottom layer generally consists of a plasticized polymeric film, felt or paper. The middle layer is the decorative portion and it often consists of polyvinyl chloride along with plasticizing agents, dyes and/or pigments, stabilizers and/or other components. In many cases this decorative layer has a cellular structure, which is achieved by decomposing a blowing agent, most commonly azodicarbonamide, during the manufacturing process. In some cases a colored design is gravure-printed on the topside of the middle layer. A discontinuous pattern of foam inhibitor can also be deposited on the topside of the middle layer in order to yield a highly textured floor covering. The upper layer is known as the xe2x80x9cwear layerxe2x80x9d and it often consists of a plasticized polyvinyl chloride or polyurethane film.
Most types of vinyl floor covering are thin and very conformable. Thus, they must be installed directly over a smooth, flat substrate. Residential sub-floors consisting of xc2xexe2x80x3 OSB or plywood sub-floor panels mounted over 2xe2x80x3xc3x9710xe2x80x3 joists are frequently abused during the home building process, and have surfaces which are often too rough and irregular to be used as a vinyl floor covering substrate. It is common practice to install a thin, smooth panel, known as an xe2x80x9cunderlayment panelxe2x80x9d, over the rough sub-floor just prior to installation of the vinyl floor covering. FIG. 1 shows a representative floor construction (10) in which a layer of vinyl floor covering (20) is adhered to a layer of underlayment panels (30), which are stapled or nailed to xc2xexe2x80x3 thick sub-floor panels (40), which span and are nailed to 2xe2x80x3xc3x9710xe2x80x3 supporting joists (50). Typical underlayment panels are sanded and comprised of plywood, particleboard, oriented strand board (OSB), or cement/fiber board. Plywood underlayments that are commonly used in North America include those derived from lauan veneer and manufactured in Indonesia and Malaysia. A plywood underlayment, known as MULTIPLY, is composed of aspen veneer and is manufactured by MacMillan Bloedel Ltd. (Vancouver, BC). Another plywood underlayment, known as TECHPLY, is composed of Russian birch veneer and is distributed in North America by the Plywood and Doors Mfrs. Corporation (Union, N.J.). A sanded xe2x85x9cxe2x80x3 thick fiberboard, known as FIBERFLOR, is manufactured by MacMillan Bloedel Ltd. (Vancouver, BC). A coated xc2xcxe2x80x3 thick OSB underlayment panel known as THE INSTALLER""S EDGE is manufactured and sold by the Weyerhaeuser Co. (Tacoma, Wash.). A xe2x85x9cxe2x80x3 thick cement/fiber board, known as FIBERBOND, is sold as underlayment by the Louisiana-Pacific Corporation (Portland, Oreg.).
All of these commercial underlayment panels have structural properties that are sufficient for an underlayment application. The panels must also have a smooth, flat, dimensionally stable, hard surface for the duration of their use in a floor system. The typical installation practice includes fastening the underlayment panels to the sub-floor by use of staples or nails; patching the seams; removing any debris from the surface of the panels; and adhering the vinyl floor covering to the underlayment by use of aqueous latex adhesives. Thus, the panels should have a solid, uniform color and appearance in order to aid in the visualization of fastener placement and surface debris when cleaning the panels. The panels must not corrode or degrade metallic fasteners. The panels must be fully compatible with conventional patching compounds and adhesives that are used during the floor covering installation process. The panels must not stain or otherwise adversely interact with the vinyl floor covering that is placed directly on top of them. Underlayment panel attributes that are particularly important and relevant to this invention include 1) compatibility with the commonly used aqueous latex adhesives and patching compounds and 2) an ability to resist staining vinyl floor coverings.
Compatibility with aqueous latex adhesives. The surface of the installed, underlayment must be receptive and functionally compatible with a large number of water-based adhesives that are used to attach the vinyl floor covering to the underlayment. Most of the adhesives are primarily comprised of aqueous acrylic or styrene-butadiene lattices, which are designed to absorb into the underlayment. Thus, the underlayment must have a surface, which will allow some penetration of a water-based adhesive.
One type of vinyl floor covering, known as xe2x80x9cfully-adheredxe2x80x9d, requires the application of adhesive across the entire underlayment surface. In this case the adhesive must be spread by use of a trowel with repeated stroking actions. Applied adhesive on one part of a floor must remain in a liquid state for a period of time sufficient for the installer to spread the adhesive across the entire floor. Thus, the adhesive must interact with the underlayment panels in a manner that results in a sufficiently long xe2x80x9copen-timexe2x80x9d. Interactions between the adhesive and the underlayment surface must not cause the adhesive to prematurely solidify. Simultaneously, bond strength must develop between the vinyl floor covering and the underlayment panel within a reasonably short time period after the vinyl floor covering has been placed in intimate contact with the adhesive on top of the underlayment. This bond strength must increase to a level that secures the vinyl floor covering to the underlayment subsequent to installation. Therefore, interactions between the applied adhesive and the underlayment surface must not impede or interfere with bond strength development.
A second type of vinyl floor covering, known as xe2x80x9cperimeter-attachedxe2x80x9d, requires application of an adhesive only at the perimeter of the floor. The perimeter-attached vinyl floor covering is laid onto the floor and positioned into the applied adhesive. In this application it is important that a strong bond quickly develop between the vinyl floor covering and the underlayment along the perimeter of the floor. Immediately after installation a volatile component in the vinyl floor covering will begin to evaporate and the floor covering will simultaneously shrink. As shrinkage occurs a strong shear stress is developed along the perimeter bond. It is vital that the bond strength along the perimeter of the floor-to-vinyl interface be sufficiently high to prevent delamination during this shrinking process.
Ability to bond with aqueous patching compounds. Patching compounds are often applied along the seams between the underlayment panels. Most patching compounds are prepared by mixing either Portland cement or gypsum with either water or an acrylic latex. Examples of commercial patching compounds that are utilized with underlayment panels and vinyl floor covering are MAPEI PLANI/PATCH from Mapei Inc. (Montreal, PQ, Canada), S-184 from Armstrong World Industries (Lancaster, Pa.) and DEPENDABLE SKIMCOAT from the Dependable Chemical Company, Incorporated (Rocky River, Ohio). It is important that these patching compounds bond to the underlayment. In general this requires that the water-based, patching compound be capable of penetrating or absorbing into the underlayment.
Ability to resist fastener corrosion. Underlayment panels are generally installed directly over structural subfloor panels and are fastened to the subfloor by use of metallic nails or staples. These metallic fasteners must not be corroded by the underlayment panel.
Ability to resist staining vinyl floor covering. Most underlayment panels for vinyl floor covering are comprised of wood laminates or composites. Wood is known to contain an array of extractives. Under conditions of elevated temperatures and high humidity some of these extractives appear to be able to migrate out of the wood and absorb into the vinyl floor covering where they can cause a stain. Underlayment composed of aspen wood appears to be particularly prone to staining vinyl floor covering. OSB underlayment, which contains aspen bark or wood isolated from the cambium layer of an aspen log is most prone to staining. Woods isolated from pine, maple, black poplar, cottonwood, walnut, hickory, elm and other species also contain extractives that are capable of staining vinyl floor coverings. Homeowners cannot remove this type of stain. Resolution generally requires replacement of the vinyl floor covering.
Some vinyl floor coverings are very susceptible to stain formation, while others are quite resistant to xe2x80x9cbottom-upxe2x80x9d staining even when they are placed in contact with an aspen substrate in an environment of high temperature and high relative humidity. In general we have found that thin, perimeter-attached type vinyl floor coverings are more prone to develop stains from contact with floor underlayment than are fully-adhered vinyl floor coverings. Also the stains observed in perimeter-attached vinyl floor covering tend to develop more rapidly and they are more intense than stains that develop in most fully-adhered vinyl floor coverings. Additionally, we have found that vinyl floor coverings with cellular decorative layers have a greater propensity to stain than do vinyl floor coverings with no cellular layer. It is suspected that plasticizing agents in the vinyl floor covering help to facilitate the transfer of extractives into the vinyl. It is further suspected that residual azodicarbonamide or its decomposition products in the cellular layer of the vinyl floor covering reacts with some wood extractives to form intensely dark products, which manifest themselves as stains.
Potential solutions to the staining problem. The vinyl floor covering manufacturers are aware of the xe2x80x9cbottom-upxe2x80x9d staining problem and they have diligently searched for a practical, cost-effective solution. The aforementioned U.S. Pat. No. 5,308,694 assigned to Tarkett describes a vinyl floor covering in which a barrier layer of plastisol and water glass are incorporated into a layer that is positioned on the bottom side of the vinyl floor covering or somewhere between the bottom side and the decorative layer. This xe2x80x9cbarrierxe2x80x9d layer reportedly prevents wooden underlayments from causing a top-side stain in the vinyl floor covering. The inventors suggest that organic stainants from the underlying floor are unable to migrate or diffuse through the barrier layer.
U.S. Pat. No. 5,891,294, assigned to Mannington, describes a vinyl floor covering in which a barrier layer consisting of a polyurethane or a polyamide is preferably positioned between the backing layer and the middle layer of the vinyl floor covering.
The inventions described is U.S. Pat. Nos. 5,308,694 and 5,891,294 appear to be too expensive to practice and these technologies have not been implemented by Tarkett, Mannington, or any of the other floor covering manufacturers.
It should also be noted that there are complications associated with applying these vinyl stain-blocking technologies to wooden underlayment products. For instance, when water glass is applied to a wooden underlayment as a coating, it forms a surface, which is not compatible with many of the conventional adhesives that are used to secure the vinyl floor sheathing during the installation process. More specifically, many latex adhesives will prematurely solidify or coagulate when applied to the water-glass coating. In fact, application of many alkaline coating systems to wooden underlayment panels generally makes the surface of the coated panel incompatible with at least some of the conventional adhesives that are used to secure the vinyl. Thus, water-glass is not suitable for use as a stain-blocking coating on a wood-based underlayment panel.
Several years ago it became known that placement of a continuous sheet of aluminum foil between a wooden substrate and the vinyl floor covering completely prevented the wood from staining the floor covering. Unfortunately, the water-based adhesives and patching compounds that are used to attach the vinyl floor covering to the wooden underlayment will not bond to the aluminum. Furthermore, the aluminum foil is expensive and susceptible to small tears or punctures. Wood extractives are capable of diffusing into the vinyl floor covering at locations in the aluminum barrier where it has been torn or perforated. Consequently, neither the vinyl floor covering manufacturers nor the underlayment manufacturers have incorporated aluminum foil barriers into their products to prevent the staining problem. Additionally, installers generally do not to position a layer of aluminum foil between the underlayment and the vinyl floor covering.
There are a number of Portland cement patching compounds that are effective stain-blocking materials when they are applied to the wooden underlayment as a top surface coating at a spread rate of about 16 wet g/ft2 or greater. Examples of such patching compounds are the previously mentioned MAPEI PLANI/PATCH by Mapei Inc. (Montreal, PQ, Canada) and ARDEX FEATHER-FINISH CEMENT produced by Ardex, Inc. (Coraopolis, Pa.). A small number of installers will apply the patching compound over the entire underlayment surface prior to vinyl floor covering installment in order to prevent the wood from staining the floor covering. Unfortunately, this practice is labor intensive and is not widely utilized. Although a Portland cement can be manufactured that could be mixed with water or an aqueous latex and then applied to the wooden underlayment by use of a roll-coating machine, the limited pot-life and high viscosity of the cement mixture makes the roll-coating machine very susceptible to fouling when the operation is conducted on a continuous, long-term basis. Also, it should be noted that the Portland cement based patching materials are highly alkaline in nature. After a 1-2 week equilibration period the cement coating becomes incompatible with a number of the conventional adhesives used to secure the vinyl to the underlayment. Thus, a Portland cement based coating appears not to be a suitable material for preparing a factory-coated underlayment panel.
Formulations that have been designed for use as primer coats over redwood, cedar or pine boards do not appear to be suitable for use as a coating over a wood-based floor underlayment panel. Such formulations are designed to be applied directly onto solid wood articles that have high concentrations of tannin, tocopherol or other intensely colored extractives. The primer formulations contain stain-blocking components, which will selectively react with and immobilize the colored extractives in the wood. Subsequent to application and drying of the primer coat, the board can be coated without discoloring the paint by transfer of the colored extractives into the paint. Although some of these xe2x80x9cpaint primersxe2x80x9d do have some ability to prevent OSB underlayment from staining vinyl floor sheathing, they generally yield a coated surface that is not compatible with many of the adhesives and patching compounds that are used in the floor installation process. Thus, the stain-blocking technologies that have been developed for paint primers are not generally suitable for application to a floor underlayment panel that is used in conjunction with vinyl floor sheathing.
One example of a paint primer formulation is that described by Thomassen in U.S. Pat. No. 5,460,644. The formulation described in this patent preferably contains a soluble zinc ammonium complex, which prevents wood extractives from staining freshly applied paint. Unfortunately, stain-blocking compounds for underlayment based on water-soluble salts are notorious for coagulating water-based vinyl adhesives immediately upon application to the underlayment.
Another example of a paint primer formulation is that described by Gilman et al. in U.S. Pat. Nos. 3,900,620 and 4,021,398. The formulation described in these patents preferably contains an aluminum hydroxychloride complex, which reportedly prevents wood extractives from staining freshly applied paint. OSB underlayment panels coated with aqueous solutions of aluminum hydroxychloride demonstrate gross incompatibility with many aqueous adhesives that are used to secure vinyl floor coverings. Aluminum hydroxychloride has little or no stain-blocking efficacy when applied to OSB panels that are used as underlayment panels for vinyl floor covering.
Yet another example of a paint primer formulation is that described by Meyer et al. in U.S. Pat. No. 4,218,516. The formulation described in this patent preferably contains magnesium hydroxide at a 1-10% level, which prevents wood extractives from staining freshly applied paint. Unfortunately, formulations that contain magnesium hydroxide at a loading level of 1-10% do not yield effective stain-blocking coatings at spread rates of 15 g/ft2 or less, which is a level that can be reasonably achieved in a commercial operation. Formulations with magnesium hydroxide concentrations of 25-30% solidify in less than one day of storage, which makes them difficult to utilize in a commercial coating operation. Stable formulations based on U.S. Pat. No. 4,218,516 are limited to magnesium hydroxide concentrations of 50% or less. Unfortunately, stain-blocking formulations that contain only 5% magnesium hydroxide must be applied at spread rates of approximately 50 g/ft2 on OSB panels in order to prevent vinyl discoloration. Such a high spread rate is not commercially feasible. An additional complication with the magnesium hydroxide-based coatings relates to the fact that aqueous suspensions of magnesium hydroxide are alkaline. Wooden panels treated with these suspensions and equilibrated for at least 1 week are incompatible with a number of the water-based adhesives that are used to secure vinyl floor sheathing.
A further example of a paint primer formulation is that described by Van Rheenen et al. in U.S. Pat. No. 5,312,863. The formulation described in this patent contains a latex with amine functionality, which prevents wood extractives from staining freshly applied paint. Application of non-complexed amines to OSB panels does not prevent the discoloration that generally occurs when the OSB is placed in contact with vinyl floor coverings.
As previously noted, the paint primer formulations were designed for an application pertaining to the wood/paint interface, which is distinctly different than that of a stain-blocker for the interface between vinyl floor sheathing and wooden OSB underlayment.
In one aspect, the present invention allows for the convenient conversion of wooden underlayment panels, especially OSB panels, that are prone to staining vinyl floor covering into coated panels that will not stain vinyl floor covering. Furthermore, this is accomplished without adversely impacting the compatibility of the underlayment panel with aqueous latex adhesives, patching compounds, metallic fasteners or vinyl floor coverings. In another aspect, a treatment process is provided that utilizes safe, single-component, liquid formulations that are stable under typical storage conditions (5-40xc2x0 C.) for at least 6-8 weeks and have Theological properties that are appropriate for commercial roll-coating and curtain-coating equipment.
Wooden underlayment panels that are prone to staining vinyl floor sheathing under conditions of elevated temperatures and high relative humidity are sequentially coated with two distinct formulations. The first formulation is applied directly on top of the virgin underlayment panel to form a coat. The formulation includes an aqueous dispersion of a copper/amine complex. Typically, this first coating is dried on the panel to form a basal (or bottom) layer (or stratum) and a second coating formulation is applied on top of the basal layer. The second formulation is predominantly comprised of water, calcium carbonate and an inert, non-ionic latex or other binder material. The applied second formulation is then dried on top of the basal layer to form a supra (or top) layer (or stratum). The coated panel is highly resistant to staining vinyl floor coverings and it is fully compatible with commonly used aqueous latex adhesives, patching compounds, metallic fasteners and vinyl floor coverings.